Vacuum speed brakes

[Vlakvark]

Hi Everyone

Was flying today (-15C) outside and coming in to land, I used the speed brakes. They only open half-way and slow to open. Decided to close them/retract but even slower on the close. Landed the plane and pushed back into hangar and brakes were still 1/3 open. My vacuum pump show in the green and all vacume gauges work fine. Any help on this. My AME said he does not know. 

Thanks

JT

[carusoam]

Are you familiar with the old plastic tubes? Age and cold weather are not friendly to them.

See if you can get them to operate properly after warming in the hangar.  If they work then, they are just sealing better when they are more pliable.  It may be easier to swap in new tubes instead of just looking for a leak.

was one side more affected than the other?

Stuff I learned about on MS, not  mechanic...

Best regards,

-a-

[Vlakvark]

I will look into the tubes. One said seem to do a better than the other side. Will new tubes be better for the cold?

[carusoam]

If they are PVC tubes, the plastic has a lot of additive to make it flexible.  Over the years the flexibilizer stuff evaporates out.  Stiff because they are old and stiff because they are cold will probably have the same result.

If they are made of a different plastic, they may not use the flexibilizer technology.

If the tubes are 40 years old, it may be best to focus on swapping them out.

Otherwise reviewing all the connections to see if you can determine which one is leaking is possible.

Start by seeing if warming them up helps.

Got any photos?

Best regards,

-a-

Edited March 10, 2017 by carusoam

[kortopates]

There are lots of threads of this topic on Mooneyspace. Google is your friend, start with this one: 

In all likelihood your conduits covering cables has disintegrated and if so these are available from Precise Flight. You can see the cables in your gear wells.

[Oldguy]

I had the left speed brake not retracting at one point and cleaned the cable in as many places as I could, deployed/retracted several times on the ground (standby vacuum pump is good for this) and have not had a problem since. All that being said, I will likely replace the cables at next year's (2018) annual.

Good news is it sounds like your vacuum pot is still working. If the diaphragm springs a leak or gets a tear, my understanding is the lack or replacement parts pretty much makes them useless.

[planedoc99]

The diaphragm in your accumulator has gone bad. Which is a major problem, as they are no longer made and completely unavailable. Precise flight does not offer them or support the vacuum brakes any longer. The only fix there is is to remove them altogether, or, install the new electrically operated speed brakes. Sorry to be the bearer of bad news. Good luck.

[Guest]

2 hours ago, planedoc99 said:

The diaphragm in your accumulator has gone bad. Which is a major problem, as they are no longer made and completely unavailable. Precise flight does not offer them or support the vacuum brakes any longer. The only fix there is is to remove them altogether, or, install the new electrically operated speed brakes. Sorry to be the bearer of bad news. Good luck.

Or send the vacuum pot to Brittain.

Clarence

[planedoc99]

11 minutes ago, M20Doc said:

Or send the vacuum pot to Brittain.

Clarence

No Joy on that one. Brittain hasn't had the diaphragm in a few years. And can't make any more, since the die was destroyed. Back to new electric ones I'm afraid

[BobAustin]

If u can find a new old stock diaphragm from the retractable step in vintage Mooneys a creative A&P can find a way to use for Vacuum Speedbrakes....so I am told...